printer code

Sleuths from the Electronic Frontier Foundation have analyzed a tracking code that's printed on every page produced by a Xerox Docucolor 12 laser printer. Many printer manufacturers embed code to give the Secret Service a tool to track counterfeiters, although it can easily be used for other purposes.

The tracking code is printed in tiny yellow dots which are generally not visibile by the naked eye under white light. Under blue light and magnified, the yellow dots appear black.

yellow dots

This is what the dots look like under 60x magnification photographed by a Digital Blue QX5 computer microscope.

Here is a magnified image of the code as it appears on a printed document.

show through

The ink for the code will show through print.

enhancing the dots

This computer graphics overlay is not to scale but it allows easier analysis of the pattern.

connecting the dots

Here's what the dots reveal: the date, time and printer's serial number on every printed page.

enhancing the dots

Bill Detwiler is Managing Editor for ZDNet's sister site TechRepublic Pro and the host of Cracking Open, CNET and TechRepublic's popular online show. He was most recently Head Technology Editor for TechRepublic. Prior to joining TechRepublic in 2000, Bill was an IT manager and desktop support technician in the social research and energy i...
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